A diode pumped high energy Yb∶‍YAG rod regenerative amplifier was demonstrated with a maximum energy of 22.3 mJ, excellent energy stability (~0.8% root mean square), and beam quality (M2 < 1.2) at 10 Hz repetition rate. To the best of our knowledge, this is the highest energy so far obtained by a Yb∶‍YAG rod regenerative amplifier.

Many organisms have developed the ability to navigate using polarized ultraviolet light of the sky. The energy and polarization of the ultraviolet (UV) band of skylight are much lower than those of the visible light, yet organisms utilize the UV band for navigation; this phenomenon is known as the "ultraviolet paradox of biological polarized light navigation". To explore the advantages of skylight polarization in the UV band, we first analyzed the single-particle scattering law based on the Mie scattering theory, studied the light transmission characteristics of clouds using the Monte-Carlo method, and finally completed the simulation of the full-sky polarization mode. The simulation results show that the UV band has a higher polarization retention after penetrating the cloud layer, and can still be used to complete navigation in unfavorable weather conditions such as cloudy and overcast skies. In this study, we demonstrate why the UV band in skylight polarization navigation is advantageous. Furthermore, the analysis of our hypothesis and study results provide guidance for the selection of the target waveband for bionic polarization navigation.

Cloud pollution can easily decrease the accuracy of satellite infrared hyperspectral observation data, leading to the loss of a large amount of observation information. In this study, a method for retrieval of temperature profile on the cloud is proposed based on observation data of FY-4A/GIIRS with cloud conditions. The radiative transfer model is used to carry out simulation experiments of observation brightness temperature under conditions of clear sky and cloud, respectively. We statistically analyze the characteristics of simulated brightness temperature changes under different channels, determine the channel selection scheme according to the cloud top pressure, and realize the retrieval of the temperature profile on the cloud through the neural network algorithm. The ERA5 reanalysis data is used as the reference standard in the accuracy evaluation of the temperature profile retrieval. The experimental results show that the overall root mean square error is better than 1.5 K, and the retrieval temperature profile has a high accuracy, which effectively improves observation data usage rate of the FY-4A/GIIRS in the cloud under pollution.

In order to extend the measurement of the nonlinear effect intensity to the fifth-order nonlinear, the fifth-order nonlinear effect in the electromagnetically induced transparency system is studied theoretically. The research results show that the quantum coherence effect greatly enhances the nonlinear effects of electromagnetically induced transparency system, including susceptibility of third-order nonlinear which can simulate Raman scattering and four-wave mixing, fifth-order nonlinear susceptibility with two completely different nonlinear absorption and dispersion.The fifth-order cross nonlinearity of the nonlinear absorption excites the four-photon absorption and the fifth-order cross nonlinearity of the nonlinear gain excites the super Raman scattering. The fifth-order cross nonlinearity of the electric polarization of the nonlinear absorption excites the six-wave mixing.

The 42D Rydberg atom is prepared in cesium vapor at room temperature, and the power-frequency electric field is measured based on the electromagnetically induced transparency spectrum of Rydberg atom. The 42D Rydberg atom is prepared by two-photon excitation, and the stepped electromagnetically induced transparency spectrum is obtained by changing the coupling frequency. The relationship between the spectral frequency shift and splitting of Rydberg atom under radio frequency(RF) electric field and the amplitude and frequency of RF electric field is studied. By modulating the amplitude of power-frequency electric field to RF electric field, the measurement of power-frequency electric field intensity and frequency is realized. Research results has important reference value and significance for online traceable measurement of power-frequency electric field.

A parallel beam will be transformed into a Bessel beam by an axicon, once the parallel beam is projected vertically onto the axicon's surface. The converted beam propagates a certain distance keeping a fixed transverse intensity distribution, which is a central circular spot surrounded by a series of dark and bright rings with proportional spacing. In this paper, first a formula is presented to evaluate the nondiffracted propagation distance according to geometrical optics principles; second, the fringe spacing of the Bessel beams is formulated using overlapping rules of optical waves, intensity distribution of the rear cross section of the axicon with exact analytic expression and the Bessel beam center spot size calculation formula are given, and the distribution of the Bessel beam is simulated by programing in MATLAB. Finally, experimental validation is given, and the relationships between the parameters of the axicon and the Bessel beam are discussed to help in utilization of the Bessel beam.

To enhance the flexibility in the optical path design of the photon chip and the optical fiber coupling and to improve the coupling efficiency, a kind of efficient vertical grating coupler based on the subwavelength line grating is designed on the premise of the Bragg condition. Finite difference time domain (FDTD) method is adopted to establish the two-dimensional structure model of the grating coupler. The effect of the structure parameters on the coupling efficiency of the subwavelength line grating coupler is systematically investigated, the physical mechanism of the line grating period, the radius and the cladding thickness influencing the coupling efficiency is analyzed, and the structure is optimized. The results show that for TE polarized incident light at 1550 nm, the coupling efficiency of over 91% can be achieved when the line grating has a period of 580 nm, a radius of 130 nm, a lower cladding thickness of 2500 nm, and an upper cladding thickness of 1400 nm. The vertical grating couplers with subwavelength line grating proposed in this paper have high coupling efficiency and simple structure, and are easily preparated, which can provide theoretical guidance and reference for the design of the grating couplers.

In this paper, we propose a method to measure the orbital angular momentum (OAM) modes of vortex beams using cubic phase gratings. Combining the unique phase change characteristics of the Airy beam with the structure function of the grating, a cubic phase grating is designed, and the vortex beam is collimated and incident on different incident points of the cubic phase grating to generate a diffraction pattern. The numerical simulation and experimental results show that the OAM mode of the incident beam can be easily measured by analyzing the Hermite-Gaussian diffraction pattern in the diffraction pattern. The topological charge of the incident beam is determined by the number of bright fringes in the diffraction pattern, and its positive and negative values are determined by the distribution trend of bright fringes. The optimized experimental link can simplify the experimental operation, the effect is obvious, and the topological load value detected can be reached up to 60.

This paper provides an optical fiber time synchronization technology based on the double fiber round-trip ratio method. The system can directly measure the unidirectional transmission delay from a master station to a slave station through the measured values of three time interval counters and the correlation ratio relationship. This method eliminates the influences of fiber length expansion and round-trip delay caused by environmental changes on the time synchronization accuracy. The master and slave stations are connected by 100 km and 75 km optical fibers, respectively. When the fiber link temperature changes from -20 ℃ to 40 ℃ and the wavelengths of 1490 nm and 1550 nm are used, the estimation error of unidirectional delay can be reduced to 260 ps, approximately. When 1310 nm and 1550 nm wavelength pair is used, the timing accuracy is improved about 1.3 ns.

Aiming at the problem that the attenuation of optical power caused by the foggy environment affects the effective communication area between vehicles, considering the size of the car and the two radiation modes of the white light car headlamps, a rectangular channel model of the space vehicle-mounted visible light communication is established. The differential element method is used to obtain the transmission power of the diffuse reflection link, and the integral idea is used to derive the attenuation coefficient of white light in the fog environment and obtain the effective working range of the system.The simulation results show that the power half-angle of the lamp, relative speed, direction of motion, road surface, surface reflective material and position of adjacent lane vehicles vary with degrees of channel attenuation, which affects the reliable transmission of information between vehicles.

To solve the contradiction between resource utilization and resource waste caused by congestion in the dual-connection offloading process, a dynamic programming algorithm with congestion prediction is proposed. Considering the high intermittent situation of millimeter wave links and fairness between heterogeneous network links under the constraint of total power, taking system weighting and rate maximization as the optimization goal, the non-convex problem is modeled as a finite-horizon discrete-time domain Markov decision process. The proposed algorithm is used to solve the power allocation problem in parallel connection of microwave and millimeter wave. The simulation results show that the algorithm can significantly improve the system performance by learning the power allocation strategy.

This paper aims at the problems of low response sensitivity and poor temperature compensation effect of fiber Bragg grating (FBG) current sensor based on giant magnetostrictive material (GMM) to propose and design a double-ring lever type GMM-FBG current sensor. First, the theoretical model of the sensor is constructed and the influence of the distance between two silicon-steel sheets on the two FBG strain differences is simulated using COMSOL software to obtain a reasonable magnetic-circuit spacing. Second, parameters are optimized for the FBG grid length. Finally, considering the magnetic-circuit spacing and the FBG grid length, the relationship between the difference of two FBG strain variables and the measured current is obtained via simulation. The results show that at 16 mm magnetic-circuit spacing and 20?70 ℃ ambient temperature, the temperature change trends on the two FBG are the same. When the FBG grid length is 10 mm, the input current is 0?100 A, and the sensitivity of the sensor is 45.4 pm/A. When the resolution of the FBG demodulator is 1.64 pm, the minimum measurable current is 0.036 A.

Under the conditions of exponentiated Weibull turbulent channel and Nakagami-m fading channel, the performance of hybrid free space optical/radio frequency (FSO/RF) communication system based on the selective combination technology is studied in this paper. Considering the pointing errors, this paper deduces the average bit error rate and outage probability of the selective combination hybrid FSO/RF communication system which adopts subcarrier modulation and intensity modulation/direct detection scheme, and obtains their new expressions by Meijer-G function and extended generalized bivariate Meijer-G function. The bit error rate and outage probability performance of hybrid FSO/RF communication system and FSO system are investigated under different subcarrier modulation schemes, turbulence intensity, pointing errors and RF channel fading parameter m. The simulation results show that the performance of the hybrid FSO/RF communication system using coherent binary phase shift keying subcarrier modulation technology is significantly better than the other three modulation technologies, and the performance of hybrid FSO/RF communication system is better than that of FSO system.

According to the complexity of photon motion under water caused by absorption and scattering attenuation, this paper establishes a photon spatio-temporal random channel model based on the tracked underwater single-photon motion state. Considering different types of water qualities, link distances, receiving apertures, launching angles, and field of view angles, the relevant information of the photons arrived at the receiving end was counted and the factors influencing optical receiving intensity and channel impulse response based on underwater single-photon communication system were studied. At the same time, comprehensively considering the photon emission, underwater photon movement process, detector characteristics, and synchronization signal extraction method, etc., a data demodulation scheme based on photon counting in the time slot was adopted and the system performance was analyzed. The simulation results show that the launching angle and receiving aperture are the main factors that affect the delay broadening. The larger the receiving aperture, the smaller the system bit error rate (BER); the larger the link distance, launching angle, and noise factor, the larger the system BER. The theoretical communication distance is about 185 m. The results well describe the characteristics of underwater photon scattering and pulse delay broadening.

An optical fiber torsion sensor based on a pre-twisted polarization-maintaining fiber (PMF) Sagnac loop mirror structure is proposed and experimentally demonstrated for simultaneously measuring rotational angle and direction. The sensing part of the structure is composed of a 2-cm pre-twisted Panda-type PMF spliced between two segments of 2-mm length multimode fiber (MMF). Torsion direction discrimination and torsion angle measurement can be realized by measuring the wavelength and power of a resonant dip in transmission spectra. The experimental results show that the sensor has a high sensitivity, and the resonant dip shifts with changes in torsion angle and direction. The wavelength of the resonant dip blue-shifts as the torsion angle increases, with a maximum wavelength sensitivity of -455 pm·rad-1·m and a power sensitivity of -1.35 dB·rad-1·m for counterclockwise torsion. For clockwise torsion, the wavelength of the resonant dip red-shifts as the torsion angle increases, with a maximum wavelength sensitivity of 182 pm·rad-1·m and a power sensitivity of 2.20 dB·rad-1·m. The sensor has the advantages of simple structure, easy fabrication, low cost, and potential applications in the field of torsion or rotation measurement.

This paper proposes a visible light fingerprint positioning scheme based on a convolutional neural network (CNN) to improve the performance of indoor visible light positioning systems. In the proposed scheme, optical intensity signals are employed as the features of the reference node LED, and receiver coordinates are employed as training labels to construct fingerprint database. In addition, a positioning model based on light intensity information is constructed, and a one-dimensional CNN learning model is adopted for training. CNN application solves the problems of low-positioning accuracy and poor stability of the fully-connected feedforward neural network method. In an indoor-positioning scene (size: 5 m×5 m×3 m), the proposed positioning scheme obtained high positioning accuracy with an average positioning error of 4.44 cm. In addition, the performance of several different indoor visible light positioning methods was compared and analyzed in simulation experiments, and the results verified the technical advantages of the proposed scheme.

In order to improve the output power of thulium-doped double-clad fiber (DCF) lasers, starting from optimizing the absorption efficiency of DCF to the pump light, pump absorption characteristics of fibers with different core diameters and inner cladding shapes are numerically simulated. The simulation results show that the pump absorption efficiency tends to 100% when the reflection times increased for the new inner clad DCFs with different core diameters. For DCFs with different inner cladding shapes, the absorption efficiency of the new inner cladding DCF is the highest. In the experiment, regular hexagonal inner cladding thulium-doped DCF and new inner cladding thulium-doped DCF are selected as the working substances. The output power of the two thulium-doped DCF lasers is 13.2 W and 14.8 W, respectively. The slope efficiency of the two thulium-doped DCF lasers is 31% and 35%, respectively. The output power of the new inner cladding thulium-doped DCF laser is 12.1% higher than that of regular hexagon inner cladding thulium-doped DCF laser, which indicates that the new inner cladding DCF is more conducive to achieve efficient pump absorption.

Pipeline transportation is one of the most important transportation methods used in the oil and gas industries. Therefore, pipeline safety monitoring is of great significance. In this paper, laser-ultrasonic visualization technology is used to detect internal defects in curved pipes. The experimental results show that the laser-ultrasonic visualization technology can intuitively detect internal defects in curved pipes through the dynamic propagation process of defect echoes. The defect location is analyzed according to the defect echo propagation rule, and the result shows that the maximum error of this method is 4%.

For the combination measurement system consisting of the laser tracker Leica AT901-MR, laser scanner Leica T-Scan5 (T-Scan), and industrial robot KUKA KR90R3100 extra, the rational planning of laser tracker stations to measure the frequently changing T-Scan pose is one of the key problems. To solve this problem, first, the construction of a combination measurement constraint model combining laser tracker and T-Scan measurement characteristics and proposing a station evaluation method to examine station viability is required. To improve the measurement efficiency and reduce the number of stations, the station planning method flow is designed based on the station evaluation method. Finally, implementing the station planning method based on Open CASCADE programming and designing a skin-scanning experiment for verification is required. The results show that the number of laser tracker stations planned by this method is less than that of the empirical method. Besides, the measurement of the skin under the planned station takes about 5 min, whereas, the empirical method takes about 40 min.

Femtosecond laser microcorrection technology is a new type of processing method that uses a laser with ultrashort pulse-width and high energy density to micromachine the gear tooth surface. Considering the mutual temperature induction between the components of the gear material, a kinetic energy thermal model of the femtosecond laser-ablated surface gear material was established, and the evolution of the temperature field of the tooth surface of the femtosecond laser-modified surface gear was simulated and analyzed. The temperature of electrons rises sharply and is much greater than the lattice temperature and the depth and diameter of ablation pits increase. The tooth surface morphology of the ablated pits was experimentally observed, confirming the correctness of the kinetic energy thermal model, and providing theoretical guidance for the study of femtosecond laser-ablated surface gears.

Using a 1064-nm picosecond fiber laser, five different energy densities were designed to conduct laser cleaning experiments on oil and rust stains present on H13 hot die steel. The results show that energy densities of 2 J/cm2 and 3 J/cm2 have the best cleaning effect; the surface roughness Ra can reach (1.1 ± 0.3) μm and (1.5 ± 0.5) μm, respectively; and the surface hardness increases to (256 ± 3.8) HV and (256 ± 2.9) HV, respectively. The main phases after cleaning are VC, (Mo, Cr)6C, (Cr, Fe)7C3, and (V, Cr)2C. In addition, the EDS results show that the contents of C, Mo, V, and Cr on the mold surface are increased.

The time-delay characteristic and effective bandwidth of semiconductor lasers produced by dual modulation of external optical injection and feedback are numerically and experimentally investigated. The experimental results show that the dual-modulated laser system has large bandwidth, and the time-delay characteristic is weakened compared with the single-modulated laser system. The experimental results have been compared to verify the obtained numerical results, indicating that the proposed scheme can improve the security performance of chaotic laser-based secure communication. Besides, more effective bandwidth and less time-delay characteristic can be obtained in the negative frequency-detuning region. The delay characteristic suppression will deteriorate in the positive frequency-detuning region.

A beam alignment system for extreme ultraviolet lithography light source system is designed to meet the requirement of beam pointing stability of extreme ultraviolet lithography light source system and ensure the conversion efficiency of extreme ultraviolet light. The alignment system is composed of two parts, the beam jitter detection module and the beam alignment module. By analyzing the beam jitter mechanism and beam control principle, a closed-loop alignment system with detection and control is built based on the virtual instrument development software LabVIEW. The experimental results show that after the beam passes through the alignment system, the jitter amplitude in the horizontal direction is less than 2 μm, the jitter amplitude in the vertical direction is less than 4 μm, and the pointing stability is less than 6 μrad, which meets the requirements of the light source system for the beam pointing stability.

Surface texture treatment can improve the wear properties of the materials. Laser processing technology is often used for the preparation of surface texture of various materials because of its advantages of high precision and high efficiency. With the development of electromagnetic technology, more friction pairs serve in magnetic field environment. In order to analyze the effect of applied magnetic field on the friction and wear of the dimple textured surface, the dimple texture is fabricated with laser on the surfaces of the 45# steel specimens, and wearing experiments are carried out under two experimental conditions, such as normal and applied magnetic field. Coefficient of friction, lubricating oil viscosity and wear mass loss of the worn specimens are measured. Worn surfaces and wear debris are observed with microscope. The experimental results show that under oil-lubricated conditions, applied magnetic field reduces the coefficient of friction, wear mass loss and adhesive wear on laser textured surface. Applied magnetic field can improve the oil viscosity, the capacity of trapping wear debris of textured dimples and the carrying capacity of oil film, which can improve the tribological properties of the laser dimple textured surface.

The human bone appears as a hierarchical structure composed of cortical bone with high density and strength and cancellous bone with low density and blood vessels. Therefore, the structure and mechanical properties of human implants should match the characteristics of human bone. Based on the stress on the natural human bone, the titanium alloy porous structure designed by topology optimization method was fabricated by laser powder bed fusion (LBPF). The mechanical properties and deformation failure mode of the porous structure were analyzed by compression experiment and numerical simulation. It was found that the numerical simulation and experimental results have a high consistency in the current work. Finally, by comparing with the mechanical properties of human natural bone, combined with the failure mode of porous structure, a porous material suitable for human implants was obtained.

In this study, selective laser melting (SLM) technology was used to produce test samples and aircraft air inlet protective grilling using TC4 powders. The microstructures and mechanical properties of printed samples were further analyzed. Results indicate that the cross section of fractured longitudinal samples has a fine microstructure, which leads to a strong fine-grain strengthening effect. Thus, superior comprehensive mechanical properties of the longitudinal samples are achieved. Moreover, the microstructure of the printed samples is found to comprise fine acicular α’ martensite. After annealing, the α’ martensites almost completely disappear. A new mixed microstructure comprising packets of the Widmannstatten and basket-weave microstructures is formed. The as-annealed samples possess high ductility and toughness with relatively inferior strength. In addition, the mechanical properties of as-annealed samples are equivalent to those of the as-forged ones. Based on the above-mentioned experimental results, the aircraft air inlet protective grilling of TC4 was prepared via SLM. The dimension precision of the unit grids is better than ±0.1 mm. Moreover, the manufacturing periodicity is reduced from seven to four days.

The low-alloy and high-strength steel D36 is joined by narrow-gap laser wire-filled welding, which results in good multi-layer and multi-pass thick plate welding without cracks, pores, and other defects after welding. The microstructure and mechanical properties of the welded joints are analyzed by the tension and bending test, microhardness test, microstructure observation, and other analytical methods. The results show that the coarse-grained heat-affected zone consists of a large number of lamellar martensite, and the microstructure of the fine-grained zone is composed of the fine-grained pearlite and ferrite. The weld center structure is proeutectoid ferrite + acicular ferrite + granular bainite. The regions with filler wire weld bead hardness in order from high to low is heat affected zone, weld center, and base material. The regions with laser primer welding hardness in order from high to low is weld center, heat affected zone, and base metal. The tensile specimens of the welded joints all fractured at the base metal position. The fracture is at an angle of 45° with the force direction, and there is obvious necking, which is a typical ductile fracture. The average tensile strength of the welds is 537 MPa, and the average elongation after fracture is 15.6%.

In order to explore the evolution law of the texture morphology under the action of multi-pulse millisecond laser, a two-dimensional symmetric model is established in this paper, which considered the influence of recoil pressure, surface tension, and evaporation rate on the change of molten pool, and is used to analyze the evolution law of the texture morphology and carry out experimental verification. The results show that under the action of recoil pressure, the depth and diameter of the pit increase with the increase of the number of pulses. The central bulge and the edge bulge are related to the thermal capillary force and Laplace pressure, and the height of bulge decreases with the increase of the number of pulses. At the edge of the molten pool, the molten material flows to the center under the influence of the thermal capillary force, and the height of the edge bulge decreases with the increase of the number of pulses.

Selective laser melting was used to fabricate a GH3536 alloy. The effects of hot isostatic pressing (HIP) and solution treatment (ST) on the microstructure, mechanical properties, and fatigue crack growth properties of the GH3536 alloy were investigated. The results show that there are molten pool, columnar grains, dendrites, holes, and cracks in the as-deposited alloy. The HIP process can effectively heal defects, eliminate molten pools and dendrites, and make all grains grow into equiaxed grains. Besides, it can lead to the continuous precipitation of carbides along the grain boundary. After ST, many carbides dissolve back into the matrix. The tensile strength, hardness, and elongation of the as-deposited alloy are 782.1 MPa, 227.9 HV, and 17.7%, respectively, and defects are essential factors affecting the plasticity. After the HIP process, the strength and hardness of the alloy decrease to 693.7 MPa and 170.4 HV, and its elongation increases to 34.7%. After the ST process, the strength, hardness, and elongation of the alloy increase to 741.0 MPa, 180.6 HV, and 48.7%, respectively. In comparison, the fatigue crack growth resistance of the as-deposited alloy is less than that of the alloy after HIP and ST are improved.

To investigate the temperature-field distribution of UO2 ceramic pellets-316Ti stainless steel composite structure during laser cutting processes, considering the relationship between thermal physical parameters and the temperature of materials, we simulated the laser cutting process for the composite structure using ANSYS finite-element software. User defined function loading and compiling of laser heat source C language program was realized using the Fluent module of ANSYS. The temperature distribution cloud maps were studied at different cutting parameters. The results show that temperature distribution is mainly expressed as comet-like state. Maximum temperature is concentrated at the center of the cutting heat source, and it increases with increasing laser power and decreasing cutting speed. When the laser power is too low or cutting speed is too high, the workpiece due to insufficient heat input will not be cut through. If the laser power is too high or cutting speed is too low, the kerf width widens due to the lager material melting area. The simulation results can be used to optimize the parameters of the actual cutting process.

A cross-polarization converter based on hollow butterfly graphene is proposed. The continuous plasmon resonance at the edge of the butterfly shape can be excited due to the surface plasmons can be supported by graphene. The proposed polarization converter can achieve excellent broadband polarization conversion performances by using a simpler structure. Numerical simulations show that when the Fermi level and relaxation time of graphene are 0.4 eV and 1.0 ps, the polarization converter can achieve a polarization conversion rate greater than 90% in the frequency range of 0.947‒1.452 THz , the relative bandwidth is 42.1%, and the center frequency is 1.2 THz. Moreover, the proposed polarization converter shows strong robustness to the incident angle of the incident terahertz wave. The polarization conversion rate can be maintained above 80% in a wide frequency range when the incident angle is increased to 40°. The high-efficiency working bandwidth and polarization conversion rate of the polarization converter can also be modulated by adjusting the Fermi level and relaxation time of graphene. This design method can have huge application potential in the field of photonics.

The damages formed in the early stage of degradation are mainly micro-cracks, and the nonlinear effect between micro-cracks and ultrasound can characterize the damage of materials. In this paper, the influence of the crack parameters on the nonlinear coefficient is analyzed theoretically based on the classical microcrack nonlinear spring model. Then, three-dimensional models of aluminum alloy plates with different crack parameters are established. High-frequency Lamb waves are used for numerical simulations to study the relationships between nonlinear coefficients and the length, width and angle. The experimental results show that as the length of the crack increases, the nonlinear coefficient increases; the width of the crack increases, and the nonlinear coefficient decreases; when three receiving probes are arranged in the Lamb wave propagation direction and the vertical directions, the three-point nonlinear coefficient changes with the angle. The angle of the crack can be roughly judged by the three-point nonlinear coefficient value. The research work is of great significance for the subsequent use of high-frequency Lamb waves to quantitatively detect the angle of micro-cracks.

Based on the imaging theory of the coaxial three-mirror optical system, a folded off-axis three-mirror optical system is designed through the aperture diaphragm off-axis and the flat mirror to fold the optical path. In the full field of view, the design value of the modulation transfer function of the optical system at the Nyquist characteristic frequency of 62.5 lp/mm is better than 0.58, and the imaging quality is close to the diffraction limit. Based on optical interference detection technology and computer-aided assembly and adjustment theory, the sensitivity matrix of primary aberration and optical component misalignment are established, and the aberration characteristics of the misaligned optical system are analyzed, and on this basis, a specific and effective optical precision assembly adjustment scheme is proposed. After the whole machine is installed and adjusted, the root mean square value of the wave aberration of the optical system in the whole field of view is better than 1/14λ(λ is wavelength). Using the camera to simulate the target at infinity, the image can be clearly imaged at the 62.5 lp/mm limit resolution of the detector, and the performance is excellent.

In water jet guided laser processing technology, high-quality beams play a key role in coupling efficiency. In order to solve the problem of water-optical coupling technology, the water jet guided laser processing technology can be better used in high-precision and low-damage processing of materials with high melting point and high hardness and brittleness, and the self-focusing-ball lens combination focusing mode and positive-negative axicons focusing mode are compared and analyzed with the traditional convex lens focusing mode. According to the three applicable focusing modes, the corresponding ABCD transmission matrix is derived, the beam characteristics under the focusing mode are simulated, and the characteristics of industrial applications under different focusing modes are discussed. The simulation results show that the beam waist radius of the combined positive-negative axicon lens is the smallest, the divergence angle of the beam after the traditional convex lens focusing mode is the smallest, and the three modes have different structures, and they all have their own advantages and disadvantages.

In order to achieve low-loss and bending-resistant mid-infrared laser transmission, the ultra-low-loss hollow-core nested anti-resonant nodeless fiber is studied in the 3 μm band, and the structural parameters of the hollow-core fiber (tube thickness, outer diameter of cladding capillary, core diameter, and nested tube outer diameter) are used for numerical simulation, and the optical fiber transmission loss as low as 0.52 dB/km is achieved in the 3 μm band. By comparing the bending loss and leakage loss of the hollow core anti-resonant fiber and the hollow core nested anti-resonant nodeless fiber, it is prove that the node-less hollow core anti-resonance fiber has lower transmission loss (loss ratio up to 22.87 dB) and better bending resistance (the loss is less than 0.1 dB/m when the bending radius is 6.5 cm) than the hollow core anti-resonance fiber.

In this study, Cu-doped Zn-In-S/ZnS core/shell quantum dot (QD) white-light-emitting diodes (WLEDs) are prepared, and the influence of the shell thickness on their properties is investigated. With several groups of QD WLEDs, the QD ratio of green and orange light is different to measure the properties of the International Commission on illumination (CIE) color coordinates, color rendering index (CRI), correlated color temperature (CCT), and luminous efficiency (LE). It is found that the LE and CRI of thick Cu‍‍∶‍Zn-In-S/ZnS core/shell QD WLEDs are higher than those of the thin Cu‍∶‍Zn-In-S/ZnS core/shell QD WLEDs. Additionally, when the thickness of the shell increases, the stability of QDs is enhanced and the luminous efficiency is increased.

The finite-difference time-domain method characterizes the near-field responses at different ends of the asymmetric nanorod structures. The results show that two modes exist in the long and short rods: low-frequency mode (LFM) and high-frequency mode (HFM). The field enhancement of the LFM at the gap end points is considerably higher than that at the outer end points. For HFM, the intensity at the gap end point of the long rod is stronger than that at the outer end point; however, the intensity at the two end points of the short rod is the same. The difference in the intensity response at different ends of two nanorods is attributed to the charge reservoir effect resulting from the different intrinsic frequencies of the nanorods. Furthermore, the oscillation frequencies of different end points are consistent at both ends of resonant nanorods and different at nonresonant nanorods. In addition, the oscillation frequency at the gap end point of the nonresonant nanorod is closer to that of the resonant frequency compared with the one at the outer point.

Surface plasmonic bending beams (SPB) are optical beams that propagate locally on metal surfaces, thus showing special application potential in photon manipulation and optical capture. Using phase matching method, various metal nanoslit arrays, including V-, N-, M-, and M+V-shaped arrays, are designed to generate the SPB. In addition, the effects of the polarization angle and structural parameters of the incident light wave on the regulation of SPB electric-field intensity are discussed. Considering the M-shaped array as a representative example, the relations between the angle of the structural arms and structural parameters and coupling between the structures on SPB are discussed. The results show that the variation in the SPB electric-field intensity generated by different structures according to the polarization angle of the incident light wave follows a sinusoidal function distribution. In addition, the SPB electric-field intensity distribution is affected by the angle between the structural arms and structural parameters and the coupling between the structures. Qualitative analyses using far-field radiation intensity of the dipole and the law of radiation angle provide guidelines for the design and optimization of SPB generators.

Mueller matrix is a type of relation matrix that describes the changes in light polarization during propagation using the Stokes vector. It is an important method for obtaining the polarization characteristics of objects. However, the measurement of Mueller matrix may be affected by factors such as the material, roughness, incident angle, and environment. In this work, multiple rotating wave plates and polarizers were used to measure the Mueller matrix of copper, aluminum, steel, silicon, and sapphire with different incident angles. The influence of the incident angle on the Mueller matrix components was analyzed. The Mueller matrix was decomposed into three matrix factors based on Lu-Chipman polar decomposition and the relationships between the diattenuation, polarizance, retardance, depolarization properties, and incident angles of samples were analyzed. The variations of m23 and m32 with the incident angle for metal and dielectric materials were found to be different; this phenomenon can be used to distinguish between metals and dielectrics. The results of this study can be used as a reference for studying the polarization characteristics of objects and identifying materials.

Unpredictable random numbers is the key to ensure the security of quantum communication. We discuss the multi-bit random number produced by the evolution of a quantum walk via the single-bit input, the preparation of multi-path coherent superposition state, and single quantum measurement. We have investigated in detail the influences of input state, precisely engineered evolution and number of evolution steps on the randomness of multi-bit quantum pure states. As for the current single-photon detection technology, quantum walks provide a good platform to increase the generation rate of random numbers.

Great progress has been made in the generation of ultrashort laser pulses in the mid-infrared (MIR) band of femtosecond laser by intra-pulse difference frequency technology, and it has been widely used in physics, chemistry, biomedicine, and other scientific areas. Firstly, the development and research background of MIR laser are introduced. Then the basic principle of intra-pulse difference frequency generation (DFG) of femtosecond laser is introduced. The progress on MIR pulse generation by intra-pulse DFG with different driving sources, such as Ti:sapphire laser, femtosecond laser at 1 μm waveband, femtosecond laser at 2 μm waveband, and fiber laser, is reviewed and compared. Finally, the future developments of the MIR femtosecond laser generated by intra-pulse DFG are prospected.

Improving the photoelectric conversion efficiency has been the main research direction in the development of solar cells. It is an effective technology and method to improve the efficiency of silicon film solar cells by using plasmon resonance effect. The enhanced scattering mechanism of plasmon generated by incident light at the metal/semiconductor interface increases light absorption for the active layer, thereby improving the energy conversion efficiency of solar cells. We introduce the working mechanism and basic parameters of solar cells; then, detail the research progress in improving efficiency of silicon thin-film solar cells based on metal nanoparticles and compound nanomaterials, plasmon, surface passivation, grating, and trapping structures. After comparing the effects and cost factors of different metal nanoparticles [i.e., gold (Au), silver (Ag), and aluminum (Al)] on the efficiency of the solar cell of monocrystalline silicon solar cells, the feasibility and application significance of using Al nanoparticles to enhance the performance of such solar cells are affirmed.

Burst-mode lasers have wide applications in nonplanar laser-induced fluorescence diagnosis, laser fine processing, and laser remote sensing detection. Based on the different key technical schemes, the research progresses of burst-mode lasers based on pulse-slicer method and pump pulse Q-switched method are summarized respectively, analyzing their technical characteristics in detail, and the development tendency of burst-mode lasers is prospected.

Owing to the existence of gain saturation and depletion, the temporal pulse shape experiences large deformations in the master oscillator power amplifier systems, resulting in large, deviation from that of the seed laser and thus an uncontrollable output shape. In order to obtain specific temporal shape in the output laser pulses, researchers have proposed the temporal pulse shaping technology in the master oscillator power amplifiers. Both the theoretical and the experimental studies are introduced to achieve proper temporal shaping in this paper. It is also pointed out that the pulse shaping can be useful in getting flexible, accurate, and extensive control over temporal features of laser pulses.

A weak-reflection fiber Bragg grating (WFBG) array has been widely concerned due to its characteristics such as single fiber tensile strength and large-scale multiplexing in recent years. These characteristics make it have potential application value in large-scale structural health monitoring and very-low-frequency (VLF) underwater acoustic signal detection. In this paper, the fabrication, demodulation and application progress of WFBG arrays are systematically reviewed. In the fabrication of WFBG arrays, the grating device is mainly with the drawing-tower Talbot and phase mask technology. In the selection of optical fibers, there are ultraviolet transparent coated fibers, cerium doped fibers, and so on. In the term of signal demodulation, it can be roughly divided into four demodulation technologies: time domain wavelength, frequency domain, microwave photons and matched interference. In the term of application, WFBG arrays can be used as a laser device or as a sensor for monitoring.

Microchannel plate (MCP) photon detectors with picosecond timing properties are expected to transform future particle physics experiments. Herein, the development and commercialization process of large-area flat-panel MCP photon detectors were briefly reviewed, the basic design elements of MCP photon detectors were summarized, and the factors influencing time resolution characteristics were analyzed. Moreover, the existing physical limitations and technical bottlenecks related to the development and commercialization of large-area flat-panel MCP photon detectors are summarized.

Liquid crystal optical phased array has been widely investigated by researchers because of its small size, simple structure, easy integration, low power consumption, and ability to automatically acquire, point, and track, meeting the requirements of future space communication and military development. This study introduces the research progress of the precise deflection of liquid crystal optical phased array beams worldwide based on the performance indicator perspective and summarizes the methods for improving performance. Furthermore, it introduces the research progress of liquid crystal optical phased array in multiple access communication and high-power laser phased-system. Finally, this study can provide a reference for the future development of liquid crystal optical phased array.

The GH3536 alloy is an important structural material for the high-temperature components of aeroengines owing to its excellent high-temperature oxidation and corrosion resistances and good performance during cold and hot forming and welding. The traditional manufacturing method of GH3536 high-temperature components has the disadvantages of long production cycle, complicated procedures, and low yield. Therefore, its production applications are limited. This study provides a comprehensive introduction to the research progress of the laser powder bed fusion of the GH3536 alloy and clarifies its structure and strengthening mechanism. Meanwhile, relevant research results were systematically investigated, conventional methods were compared, and the preparation of GH3536 alloy by laser powder bed technology is comprehensively discussed from the aspects of technical principle, microstructure, and mechanical properties. Furthermore, the composite technology of additive and traditional manufacturing is investigated. Finally, the future application and development trends of the GH3536 alloy prepared by laser powder bed technology are discussed.

Laser-induced breakdown spectroscopy (LIBS) combined with conventional tablet preparation methods for detecting cadmium (Cd) content of rice has low sensitivity. This study proposes to use a film sample preparation method to improve the sensitivity of LIBS to detect the Cd content in rice. A rice film sample was prepared after scraping the rice suspension onto a glass slide, and the feasibility of using the film sample to improve the sensitivity and accuracy of Cd content detection in rice was discussed. For the tablet and film samples, the spectrometer's delay time and laser energy were improved, and the reasons for the inconsistency of the optimal laser energy were analyzed. After optimizing the experimental conditions, the differences between the LIBS spectra of the tablet and film samples were compared, and the principle of film enhancement was analyzed through experiments. The Cd-spectrum intensity of film preparation increased 5-7 times compared to the conventional tablet preparation, and the detection limit is reduced by 1/9. The method of film preparation improves the ability of LIBS technology to detect Cd content in rice.

In this paper, a CO2 laser is used as the heating source to study the rapid pyrolysis process of solid fuel (coal and Eucalyptus) particles in an argon atmosphere. Laser-induced breakdown spectroscopy (LIBS) technology is applied to study the temporal and spatial distribution characteristics of pyrolysis products (including C, H, O, CN, and C2). The experimental results show that the pyrolysis process of coal and Eucalyptus presents two stages, namely the dehydration and desorption stage and the macromolecular decomposition stage. In the dehydration and desorption stage, Eucalyptus thermally desorbed more carbon and nitrogen components than coal; in the macromolecular decomposition stage, the peak time of the precipitation of various elements in Eucalyptus is significantly later than that of coal. Besides, in the macromolecular decomposition stage, the proportion of H and O in the volatile components precipitated by Eucalyptus is larger, and the proportion of CN and C2 in the volatile components precipitated by coal is larger. It can be seen from the ratio of residual energy and H spectral intensity value to C spectral intensity value that the change rule of the two presents a good consistency, which proves that the distribution of macromolecular components such as tar is closer to the fuel surface, and the concentration of small molecular gas components increases with height above the sample surface.

In response to the need for rapid calibration of the domestic accelerator beam and referring to the single event rollover monitor of European Space Agency, this paper successfully developed a heavy ion single event effect calibration system and successfully applied it to the domestic tandem heavy ion accelerator beam single event test calibration. The test results show that 11 kinds of heavy ions can be calibrated to the SEU (Single Event Upset) cross-section data of the system in the "00" and "FF" data modes under the irradiation angles of 0°, 45° and 60°, respectively. By comparing with the results of single-event flipping test data of major accelerators at home and abroad, the physical distribution of single-event flipping inside the calibration system is analyzed, which verifies that the designed single-particle calibration system can accurately monitor the accuracy and uniformity of the heavy ion accelerator beam.